Lens logic: If many process lenses are symmetrical, can they be convertible (using 1/2), or does it depend on the design?

DREW WILEY

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The first predictable color processes arrived with the invention of panchromatic black and white film. But the first color photos per se were actually Daguerrotypes. A few still exist. But since the color result was accidental and extremely rare, it could not be repeated, even today. My hunch is that, due to poor quality control, some of the chemicals involved contained unknown contaminants leading to that.
 

MarkS

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It's worth noting that Schneider made their f/5.6 Symmar lenses as convertibles; you would remove the front group to get the longer f.l. that was marked in green on the nameplate ring. Those were made c.1955-72? and are easy to find on the used market. Very good lenses, too, when not converted. I used several on the job in the '80s-'90s, but never messed with the conversion.
But when Schneider introduced the Symmar-S series in the early '70s, they did not offer the lenses as convertibles- indeed in the introductory brochure they mentioned discontinuing the convertible feature, in order to improve the optical performance of the complete optic. And of course, the Symmar-S lenses have a fine reputation for resolution and contrast.
 

DREW WILEY

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I preferred the Symmar S to later plastmats for portraiture etc due to their gentler edge rendering. They were sufficiently sharp, but certainly not as well corrected as the Fuji and Rodenstock equivalents that were beginning to show up, then Nikon too. Eventually Schneider redid their own. A modern convertible is offered by Cooke, but at high price and on a pre-order wait basis.
 

Donald Qualls

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DREW WILEY said:
the first color photos per se were actually Daguerrotypes.
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I always thought color in a Dag (which I've seen in modern ones, but again not consistently) was the same phenomenon as a Lippman plate -- the reflective silver producing interference layers in the halide layer. I could be wrong, though, I don't know that I've seen a definite analysis. At least some Dags were hand colored, too.
 

DREW WILEY

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I'm not referring to hand-coloring, which was quite common. Precise molecular analysis might potentially involve destructive sampling of portions of these extremely rare images, or exposure to excessive illumination. There might be more sophisticated sampling options today; but overall, they've been kept off display and carefully locked up for a reason. Photographic copies of them have been made. These pre-date Lipman by quite a ways, but might have certain things in common. One of these being mercury, it's easy to see why people are reluctant to experiment.
 

Donald Qualls

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It occurred to me the other day, just after my last reply that one might be able to reproduce Lippman plates without the mercury (which works well but people are afraid of) or galinstan (which doesn't work particularly well due to the stickiness of gallium) by coating liquid emulsion onto a silvered or aluminized surface (glass or copper like a Dag plate). Expose and develop, then (optionally?) transfer the emulsion to a conventional base for viewing.

Coating directly on the silver would give the tightly coupled reflective surface Lippman needs, but I'm not certain how well it would work to free the emulsion from the silver after development. I envision bonding a sub-coated sheet to the emulsion, then gently heating the plate substrate from the back side.

The first part of this, at least, could be managed with Liquid Light (etc.) coated on a small surplus first surface flat mirror (fairly cheap from Surplus Shed). That would be within reasonable resources for initial experiments...
 

Nodda Duma

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Nick Brandredth has successfully made Lippmann Plates showing color. I have one of them that he sent me packed away somewhere.
 

Donald Qualls

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Nodda Duma said:
Nick Brandredth has successfully made Lippmann Plates showing color. I have one of them that he sent me packed away somewhere.
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Was he the fellow using galinstan (the alloy used in post-mercury metal column thermometers)? I read a fairly in-depth article about the problems with galinstan (because gallium has several important difference from mercury beside toxicity).
 

DREW WILEY

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Interesting. Our local chemical house, Bryant Lab, was mainly a pharmaceutical plant and hospital lab supplier, but also had one of the best selections of photo chem in the country. They were just five minutes away from my office. When the original phD owner retired, two of his assistants, who both had recent phD's specializing in Gallium research, purchased the business and were doing well. It sure would have been interesting to discuss this subject with them, since all kind of both alt photo types as well as artsy metal plating types shopped there. But right around the same time, gallium applications were becoming an especially hot topoc in local chip-related R&D industries. And they were both offered so much pay they couldn't resist; so that was the end of the chemical business.

Nearby was a surprisingly large warehouse space devoted exclusively to thermometers - all kinds of them, which in a University town, and amidst all kinds of Biotech and pharmaceutical plants, supplied the need for specialized scientific thermometers. But some of the ones up at the LBL rad lab, capable of measuring in millionths of a degree, were built in-house. The fellow who worked there looked more like a walking-dead pale nosferatu than the movie versions. Don't think he ever went out into sunlight, and perhaps spent his nights there in a coffin.
 
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Petrochemist

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Many early lenses used symmetrical designs to reduce aberrations.
The lenses sold for convertible use almost certainly consist of two lenses both designed to work as individual units, but there's no reason not to try lenses with elements or groups removed.
One of the SLR lenses I brought cheap had severe fogging in the rear elements & it turned out my efforts at cleaning it didn't solve matters. In the end I simply removed the rear group entirely & added extra extension so the revise lens would focus. Results may not be quite as sharp as the original lens but they are certainly quite usable.

Others have removed groups & flipped elements from many normal primes specifically to get a soft focus lens.

Shooting experiments like this may not be as cheap on LF as on digital systems, but if the results are truly dire you'll see as much on the ground glass. So as long as you can meter determine the new f-stop, you'll only waste film if it's bad but not dire
 

Donald Qualls

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Petrochemist said:
Shooting experiments like this may not be as cheap on LF as on digital systems,
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Surely not, but costs can be controlled. Ortho litho films can be processed to pictorial contrast, and are very cheap. X-ray film is cheap if you can cut it down from the usual large sheets to fit your film holders in your own darkroom. Paper negatives are cheap. Even Fomapan, a good traditional film stock, is less than half the price of Kodak or Ilford 4x5.

Even in an 8x10 camera, these sources can control costs and make experimenting with converting a process lens affordable, as long as you can process your own film.
 

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Murrayatuptown

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If a conservator gets involved for historically significant items, they can get pretty restrictive. I've read of limitations of 15 footcandles and restriction number of hours of illumination, storing elsewhere when not part of an exhibit.

They may use same protocol for a variety of items depending on value or significance. I think they probably lean toward caution regardless of monetary value because items may be on loan from another owner, or simply easier to protect than the alternative(s).
 
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Murrayatuptown

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But the lens...

I was able to put the rear cell into a reduced i.d. M39-M42 double-threaded adapter. I had a machinist drill 4 holes in an M42/C-NEX adapter (because it worked) that aligned with 4 on the front cell saying that centering was the most important concern I had. The rear cell spacing is now within 0.001" of its original distance. I know centration is determined optically, not by trusting a machinist.

I can't be certain of the exact front-rear cell spacing because the barrel was bent at the shutter slot, causing two measurements.

It's also wide open right now (f/10), but normally used at f/45 or higher (had f/10-256 range).

It's a rescue experiment. Hopefully better than a magnifying glass.

Step at a time...
 
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Murrayatuptown

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I get the feeling (from reading) that adding a front or rear auxiliary stop because I cannot (at this stage) insert anything at exactly the original distance may or may not have the same deleterious effects as incorrect intended 'central' location (integral to the lens design).

A supplemental external stop may create different problems like reduction of format capability (possibly severely), or other 'weird phenomena' not in the list of aberrations...some defect that can be diagnosed and named if visible.

Again, 'salvage', not 'restoration'.

I think I may have something that will be 'artistically usable' but never expect it to be what it once was.
 

Dan Fromm

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Murray, why don't you stop theorizing and start experimenting?
 
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